As new methods for diagnosis of infectious diseases develop, it is necessary to evaluate their performance in a particular hospital setting. There are now available new blood culture systems which permit automated 24 hour surveillance of incubating blood culture bottles. The BacT-Alert is the earliest model commercially available. We are currently assessing the advantages or disadvantages of this new technology for detection of sepsis in Clinical Center patients. Results will compared to our current standard method, a lysis-centrifugation procedure (Isolator). This study will require several hundred positive blood cultures in order to determine the sensitivity, specificity, advantages, and disadvantages of the different blood culture methods.